The discovery of letters left by an elderly couple who checked into a luxury Paris hotel to commit suicide has reopened the debate in France about the right of individuals to choose to die.

Georgette and Bernard Cazes, 86, were found lying peacefully holding hands on a bed in a room at the Lutetia hotel in the left-bank Saint-Germain district, having planned their deaths in meticulous detail.

Police found two documents in the room, which was undisturbed: one, a letter for the couple's family; the other, a typewritten missive addressed to the French public prosecutor demanding "the right to die in a dignified manner".

In it Georgette Cazes voiced her anger at not being allowed to leave the world "peacefully" and declared her letter a formal legal complaint for the "non respect of my liberty".

She wrote that she had asked her son to pursue the case after her death.

He told Le Parisien newspaper, which published romantic black and white pictures of the Cazes as youngsters walking hand in hand through Paris, that his parents had been planning their double suicide "for decades".

"They feared being separated and being dependent a lot more than they feared death," he said.

The story of Georgette and Bernard's life, love and death has touched more than hearts here in France, where euthanasia is the next battleground for the country's traditionally conservative Catholic community, still furious over recent legislation allowing same-sex marriage.

Euthanasia is illegal in France, but Socialist president François Hollande made changing the law one of his 2012 election campaign pledges.

Various opinion polls have suggested the French public broadly supports euthanasia. A recent survey by Ifop found 92% of those asked believe assisted suicide should be allowed for those suffering from an incurable or terminal illness.

A six-month study last year recommended that "active euthanasia", deemed an act by a third person intended to cause death, should remain banned. And members of an ethics committee consulted by the government announced earlier this year that a majority of its members opposed any legalisation allowing any form of euthanasia or assisted suicide.

In her letter, Georgette Cazes criticised the law "banning access to any lethal pill that would allow a gentle death". She added: "Isn't my liberty being limited by that of others? What law prevents a person who has no responsibilities, whose tax affairs are in order, who has worked all the years she wanted and then carried out voluntary work in social services, what law forces her into cruel practices when she wants to leave life peacefully?"

After checking into The Lutetia on Thursday evening, the Cazes, who had been inseparable since they married as student sweethearts sixty years ago, ensured their bodies would be discovered quickly by ordering a room-service breakfast for the following morning.

The pair, who met as students in post-war Bordeaux and were described as "brilliant intellectuals", had two sons. The youngest, Vincent, died in a car accident in 1976 aged 21.

Their elder son, who was not named by Le Parisien, explained his parents had chosen the palatial Art Déco hotel, popular with Pablo Picasso and Little Prince author Antoine de Saint Exupéry, because it was where Georgette Cazes was reunited with her father when he returned to France after five years in a German prison camp duringthe second world war.

A former Latin professor, Georgette wrote school books and was involved in voluntary work teaching French during retirement. Her husband, an economist and philosopher, was a high-ranking civil servant and wrote books and literary reviews.

An official inquiry by a "citizens' committee" into the subject is expected to be published on 16 December and Hollande has said a parliamentary bill on assisted suicide may be introduced in the Assemblée Nationale before the end of the year.